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  <div class="section" id="module-asyncio">
<span id="asyncio-asynchronous-i-o"></span><h1><a class="reference internal" href="#module-asyncio" title="asyncio: Asynchronous I/O."><code class="xref py py-mod docutils literal notranslate"><span class="pre">asyncio</span></code></a> — Asynchronous I/O<a class="headerlink" href="#module-asyncio" title="Permalink to this headline">¶</a></h1>
<hr class="docutils" />
<div class="sidebar">
<p class="first sidebar-title">Hello World!</p>
<div class="last highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">asyncio</span>

<span class="k">async</span> <span class="k">def</span> <span class="nf">main</span><span class="p">():</span>
    <span class="nb">print</span><span class="p">(</span><span class="s1">&#39;Hello ...&#39;</span><span class="p">)</span>
    <span class="k">await</span> <span class="n">asyncio</span><span class="o">.</span><span class="n">sleep</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
    <span class="nb">print</span><span class="p">(</span><span class="s1">&#39;... World!&#39;</span><span class="p">)</span>

<span class="c1"># Python 3.7+</span>
<span class="n">asyncio</span><span class="o">.</span><span class="n">run</span><span class="p">(</span><span class="n">main</span><span class="p">())</span>
</pre></div>
</div>
</div>
<p>asyncio is a library to write <strong>concurrent</strong> code using
the <strong>async/await</strong> syntax.</p>
<p>asyncio is used as a foundation for multiple Python asynchronous
frameworks that provide high-performance network and web-servers,
database connection libraries, distributed task queues, etc.</p>
<p>asyncio is often a perfect fit for IO-bound and high-level
<strong>structured</strong> network code.</p>
<p>asyncio provides a set of <strong>high-level</strong> APIs to:</p>
<ul class="simple">
<li><a class="reference internal" href="asyncio-task.html#coroutine"><span class="std std-ref">run Python coroutines</span></a> concurrently and
have full control over their execution;</li>
<li>perform <a class="reference internal" href="asyncio-stream.html#asyncio-streams"><span class="std std-ref">network IO and IPC</span></a>;</li>
<li>control <a class="reference internal" href="asyncio-subprocess.html#asyncio-subprocess"><span class="std std-ref">subprocesses</span></a>;</li>
<li>distribute tasks via <a class="reference internal" href="asyncio-queue.html#asyncio-queues"><span class="std std-ref">queues</span></a>;</li>
<li><a class="reference internal" href="asyncio-sync.html#asyncio-sync"><span class="std std-ref">synchronize</span></a> concurrent code;</li>
</ul>
<p>Additionally, there are <strong>low-level</strong> APIs for
<em>library and framework developers</em> to:</p>
<ul class="simple">
<li>create and manage <a class="reference internal" href="asyncio-eventloop.html#asyncio-event-loop"><span class="std std-ref">event loops</span></a>, which
provide asynchronous APIs for <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.create_server" title="asyncio.loop.create_server"><code class="xref py py-meth docutils literal notranslate"><span class="pre">networking</span></code></a>,
running <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.subprocess_exec" title="asyncio.loop.subprocess_exec"><code class="xref py py-meth docutils literal notranslate"><span class="pre">subprocesses</span></code></a>,
handling <a class="reference internal" href="asyncio-eventloop.html#asyncio.loop.add_signal_handler" title="asyncio.loop.add_signal_handler"><code class="xref py py-meth docutils literal notranslate"><span class="pre">OS</span> <span class="pre">signals</span></code></a>, etc;</li>
<li>implement efficient protocols using
<a class="reference internal" href="asyncio-protocol.html#asyncio-transports-protocols"><span class="std std-ref">transports</span></a>;</li>
<li><a class="reference internal" href="asyncio-future.html#asyncio-futures"><span class="std std-ref">bridge</span></a> callback-based libraries and code
with async/await syntax.</li>
</ul>
<p class="rubric">Reference</p>
<div class="toctree-wrapper compound">
<p class="caption"><span class="caption-text">High-level APIs</span></p>
<ul>
<li class="toctree-l1"><a class="reference internal" href="asyncio-task.html">Coroutines and Tasks</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-stream.html">Streams</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-sync.html">Synchronization Primitives</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-subprocess.html">Subprocesses</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-queue.html">Queues</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-exceptions.html">Exceptions</a></li>
</ul>
</div>
<div class="toctree-wrapper compound">
<p class="caption"><span class="caption-text">Low-level APIs</span></p>
<ul>
<li class="toctree-l1"><a class="reference internal" href="asyncio-eventloop.html">Event Loop</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-future.html">Futures</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-protocol.html">Transports and Protocols</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-policy.html">Policies</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-platforms.html">Platform Support</a></li>
</ul>
</div>
<div class="toctree-wrapper compound">
<p class="caption"><span class="caption-text">Guides and Tutorials</span></p>
<ul>
<li class="toctree-l1"><a class="reference internal" href="asyncio-api-index.html">High-level API Index</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-llapi-index.html">Low-level API Index</a></li>
<li class="toctree-l1"><a class="reference internal" href="asyncio-dev.html">Developing with asyncio</a></li>
</ul>
</div>
</div>


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